1. Field of the Invention
The present invention relates to a conducting belt for use with an anode holder and an anode holder, and more particularly to a conducting belt for supplying an electric current to an anode for plating a surface of a substrate such as a semiconductor wafer, and an anode holder for holding such an anode. The present invention is also concerned with a plating apparatus for plating a substrate using the conducting belt. The plating apparatus may be a bump plating apparatus for forming bumps on a surface of a semiconductor substrate or a plating apparatus for plating via holes having high aspect ratios and large depths, e.g., a diameter of 10 μm to 20 μm and a depth of 70 μm to 150 μm.
2. Description of the Related Art
In recent years, there has been used a method of forming metal films and organic films on substrates such as semiconductor wafers by a plating process in forming semiconductor circuit interconnections and bumps. For example, it has widely been practiced to form bumps (protruding connecting electrode) or interconnections of gold, silver, copper, solder, nickel or a multilayer of these metals at predetermined portions on a surface of a semiconductor wafer having semiconductor circuits and fine interconnections for connecting semiconductor circuits, thereby electrically connecting the semiconductor circuits via the bumps to electrodes of a package substrate or tape automated bonding (TAB) electrodes. The interconnections and the bumps may be formed by any of various methods including an electroplating method, an electroless plating method, a vapor deposition method, and a printing method. Of these methods, the electroplating process has been used most widely because it can produce finer patterns at a higher film deposition rate to produce semiconductor chips with more I/O terminals and smaller pitches. For details, reference should be made to Japanese laid-open patent publication No. 2000-96292. Metal films formed by the electroplating process that are most widely used have characteristics of high purity, high deposition rate, and easy film-thickness control.
FIG. 15 of the accompanying drawings schematically shows a vertical-immersion plating apparatus in which a substrate and an anode are vertically placed in a plating tank. As shown in FIG. 15, the plating apparatus includes a plating tank 101 containing a plating solution Q therein. An anode 103 held by an anode holder 102 and a substrate W held by a substrate holder 104 are vertically immersed in the plating solution Q in such a manner that the anode 103 and the substrate W are spaced in confronting relation from each other and lie parallel to each other. When an electric current is supplied between the anode 103 and the substrate W by a plating power supply 105, a surface W1 of the substrate W which is exposed from the substrate holder 104 is electroplated. The plating tank 101 is combined with a plating solution circulator 106 for circulating the plating solution Q by supplying the plating solution Q from an inlet port 111 into the plating tank 101 and discharging the plating solution Q from the plating tank 101 through an outlet port 112.
As shown in FIG. 15, the vertical-immersion plating apparatus performs plating of the substrate W by placing the substrate W so as to face the anode 103 that is held by the anode holder 102. Although a plate-like anode is shown as an anode, an anode ball housed in a cage may be used as an anode. However, the plate-like anode held by the anode holder offers the following advantages:
1) A shield plate may be mounted on the anode holder, and such shield plate may make it possible to adjust the opening diameter of the anode, thereby easily controlling in-plane uniformity (see, for example, Japanese laid-open patent publication No. 2005-29863).
2) Because the anode is in the form of a plate, the anode can easily be held parallel to the substrate to improve in-plane uniformity.
As described above, using the anode holder to hold the anode while the substrate is being plated by the vertical-immersion plating apparatus is advantageous. However, the plating apparatus is required to have the following functions in order to meet growing demands for finer interconnections and increased throughputs:
1) Finer interconnections to be formed on substrates require certainty of supply of an electric current to the anode.
2) As the substrate to be processed is larger in size, the anode is also larger in size. Since the larger anode cannot easily be replaced manually with another anode due to their weight, a new jig is needed for anode replacement.
3) The replacement of the anode needs to be performed efficiently in a short period of time.